Biodegradable, anti-freezing and self-healable hydrogel mulch film for weed control

Hydrogel is widely used in agriculture as water retention agent and fertilizer delivery vehicle due to its highly porous and hydrated structure. Hydrogel loses water gradually and becomes fragile, which greatly hinders its potential application as mulching film for weed control as the weeds can penetrate the weakened hydrogel film easily. Here, we report a self-healable and biodegradable hydrogel (COCu-K) mulching film composed of chitosan derivatives, copper-doped carbon dots (Cu-CDs) and KCl for weed inhibition. The dehydrated COCu-K hydrogel fragments spread on top of soil self-heal in-situ into an integrate hydrogel film by simple watering, preventing the germination and growth of weeds. SEM reveals the well-dispersed multi-hierarchical structure on the surface of COCu-K hydrogel. The effects of dosages of KCl and Cu-CDs on the hydrogel structure and consequent performances of hydrogel mulching film including self-healing, anti-freezing, weeds inhibition have been explored. The pot experiments illustrated a weed seeds inhibition ratio of 90% and strengthened growth of pepper seedlings induced by the best practice hydrogel COCu0.08-K2.5. Meanwhile, the COCu0.08-K2.5 hydrogel shows an outstanding degradability with a degradation rate of 63.61±3.26% within eight weeks, and soil containing degraded COCu0.08-K2.5 hydrogel presents no phytotoxicity. This study provides a facile and viable strategy to design and utilize hydrogel mulching for weed control.